152 BOTANICAL GAZETTE [AuGUST 
the jacket cells into the egg could be detected. The ventral canal cell is 
formed about a week before fertilization, which, in the neighborhood of 
Ithaca, occurs about the middle of June. No walls are formed in the proem- 
bryo until it has reached the eight-celled stage. Strasburger described 
walls at the four-celled stage, and other writers have described walls at the 
four-celled stage in Pinus, 
The antheridial cell of Strasburger (third prothallial cell of Belajeff) is 
called the central cell by Miyake, who regards it as the equivalent of the 
central cell in the antheridium of pteridophytes. The body cell of Stras- 
burger is called the generative cell. Strasburger refers to the two male cells 
as generative cells. The terminology is confusing and we are not sure that 
the present writer has been entirely consistent.— CHARLES J. CHAMBERLAIN. 
PLANT HYBRIDS have received but little attention from cytologists. It 
is known that various species of a genus usually have the same number of 
chromosomes and that the pollen of sterile hybrids usually have imperfect 
pollen. Rosenberg” has been fortunate in finding a hybrid between parents 
which differ from each other both in the number and size of their chromo- 
somes. This hybrid is Drosera rotundifolia < longifolia. D. rotundifolia has 
twenty chromosomes in the sporophyte, this number appearing in the stem, 
leaf,and root. The chromosomes are short and easy to count. In the pollen 
mother-cell the number is always ten. In D. /ongifolia the vegetative tissues 
show forty chromosomes and the pollen mother-cells twenty, just double the 
numbers in the other species. The chromosomes are also distinguished by 
being somewhat smaller than in D. rotundifolia. 
The hybrid is easily recognized by external characters, but is also dis- 
tinguished by its chromosomes. The mitoses are not different from those of 
the parents except in the number of chromosumes and the consequent varia- 
tion in the shape of the spindle. In the sporophyte thirty chromosomes, the 
sum of the gametophyte numbers of the two parents, was counted in the 
root, stem, and leaf. In a few cases forty chromosomes appeared in the 
tapetal cells. In the pollen mother-cells fifteen chromosomes is the domi- 
‘ nant number, but twenty often occur, and occasionally mother-cells with ten 
are found. All three numbers ‘have been found in the same anther. The 
megaspore mother-cell was not investigated. 
The relative number of chromosomes in the parents and hybrid support 
the theory that the chromosome is a permanent organ of the cell. The fact 
that three kinds of pollen grains are formed has its bearing upon Mendelism. 
Professor Rosenberg will continue these investigations.— CHARLES J. CHAM- 
BERLAIN. 
IN THE FIRST of a series of studies on the anatomy of ferns, entitled 
“La masse libéroligneuse élémentaire des Filicinées actuelles et ses princi- 
7 ROSENBERG, O., Das Verhalten der Chromosomen in einer hybriden Pflanze. 
Ber. Deutsch. Bot. Gesell. 21: 110-119. A/. 7. 1903. 
